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Electroorganic Synthesis, 54. Enantioselective Cathodic Reduction of 4‐Substituted Coumarins with Alkaloids as Catalysts, 1
Author(s) -
Schoo Norbert,
Schäfer HansJ.
Publication year - 1993
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.199319930198
Subject(s) - enantioselective synthesis , chemistry , cathodic protection , catalysis , combinatorial chemistry , reduction (mathematics) , organic chemistry , electrochemistry , electrode , geometry , mathematics
The optical yield in the alkaloid‐catalyzed enantioselective electroreduction of 4‐methylcoumarin ( 1a ) was increased from 17% to 47.4% by systematic variation of the electrolysis conditions. The results are explained by an induction mechanism in which the adsorbed protonated alkaloid acts as a chiral proton donor towards a prochiral carbanion derived from 1a . The preferred configuration of the product and the results obtained by variation of the alkaloid structure allow us to propose a model of the transition state. Furthermore, 4‐phenylcoumarin ( 1b ) and 4‐(trifluoromethyl)coumarin ( 1c ) were reduced with 13.2% and 8.4% ee, respectively.